Fusion of the spine is a well-known and widely practiced medical procedure to alleviate severe back and/or neck pain due to misaligned, damaged or otherwise diseased spines. In some cases, the fusion is carried out by implanting a cage, or implantable device having an opening for the ingrowth of tissue therethrough, at the level of the spine to be fused. The opening may be filled with, or contain, bone graft material, bone chips or other biologically active material that enhances fusion.
Where it is difficult to maneuver and insert a rigid implantable device due to the size limitations or delicate anatomical site (i.e., closeness to nerves or spinal cord, e.g.) of the area to be implanted, it is desirable to provide an implant that may be converted from a flexible implant into a rigid one that can promote fusion. Expandable fusion cages are well known in the art. Most of these fusion cages comprise two or more components that cooperate together to form a fusion promoting device. For instance, a typical expandable spinal implant can comprise a flexible fusion cage and a corresponding insert that, when inserted, expands the fusion cage.
As further examples of expandable spinal implants, U.S. Patent Application Publication No. 2010/0234956 entitled “EXPANDING CAGE FOR VERTEBRAL SURGERY” to Attia et al. describes an expanding intervertebral implant comprising an intervertebral fusion cage and an insertable rod for placement inside the cage to expand the cage after implantation. U.S. Pat. No. 7,578,849 entitled “INTERVERTEBRAL IMPLANTS AND METHODS OF USE” by Trieu described another two-component intervertebral spinal stabilization implant having a fusion cage and an elastic component for insertion into the fusion cage. U.S. Pat. No. 6,102,950 entitled “INTERVERTEBRAL BODY FUSION DEVICE” by Vaccaro describes a two-component fusion promoting implant comprising an intervertebral body fusion device having a cage component for placement intervertebrally, and a wedge body that is insertable into the cage component.
However, these expandable spinal implants are not intended for use without their inserts. In other words, these implants are not configured for conversion from a functional dynamic implant into a fusion implant at a later time.
Dynamic implants having the desired anatomical shape and size conducive for dynamic spinal stabilization are known. One such implant is described in U.S. Pat. No. 7,867,276 entitled “DYNAMIC INTERVERTEBRAL IMPLANT” by Matge. However, this dynamic intervertebral implant is not configured to be easily converted into a fusion promoting implant at a later time.
Accordingly, there exists a need for a modular, convertible implant system that can be used in either dynamic or fusion-promoting modes, or both, at different points of time.